LED Lighting

Background

Back in August 2011, I had ordered 2 packages of LEDs, ultra-bright white and warm white, 200 count each, to experiment with LED lighting. In this post I will document what worked, but more importantly, what did not work.

As far as home lighting goes, you will get the most amount of light from halogen light bulbs, but they are very inefficient. Most of the energy is converted to heat. In fact, one time a halogen light bulb in our torch lamp got so hot that, it exploded and shards spread all over the carpet. More on that later.

Then there is the regular incandescent light bulbs. We still use several of these where we can not use fluorescent ones.

Fluorescent and Compact Fluorescent Lights(CFLs) are very efficient and give out lots of light. One annoyance with CFLs is that they are not very bright when first turned on. Also they fail often due to inverter problems.

LED lighting is the newcomer to the scene. LEDs are lot more efficient than fluorescent lights, but do they work? One big difference of LEDs to the previous category of light bulbs is that the light produced is directional. It looks super bright if you are looking directly at them, but you see very little light from other angles. On the plus side, the LED lifetime is better than anything else out there.

Torch Lamp

After the halogen light bulb explosion I mentioned above, I had already converted our torch lamps to circular fluorescent light bulbs. Why not go a step further and convert them to LED lights?

I took a foam and cut it as shown in the picture below and installed warm light LEDs all around, 10 LEDs to each string.There is supposed to be a total of 200 LEDs, but as you can see in the picture 5 are missing. I had used them elsewhere. I replaced them with resistors.

Here is how the backside looks like, not so pretty. 10 LEDs in each string are connected in series, and 5 strings are connected in series (total of 50 LEDs). Four of those are connected in parallel (makes 200 in total). Voltage needed to operate = 50 * 3.2 = 160VDC.

The power supply is a bridge rectifier and a capacitor.

Here is how it looked like when turned on. The lamp worked fine, but with several problems. The first problem was that it was not quite as bright as the fluorescent light bulb. The second problem was that there was a little bit of flicker. The third problem was that there was too much labor involved to build it.

Because of the problems I listed above, I dismantled this lamp and decided to scale back and moved on to a simpler project. However, I did not totally give up on indoor LED lighting. I will order more powerful LEDs for testing (at least 5 watts, and up).

Desk Lamp

This project was moderately successful. In this project I used white lights instead of warm lights. Here is the picture of the original fluorescent light bulb and the LED version.

Again 10 LEDs in each string and there are 5 strings in total. The difference here is that each string has 68 ohm resistor connected in series to equalize each string. Otherwise, because of the variations in LEDs, one string would draw more current than the remaining four. These 50 LEDs made one block.

I made another block identical to the first one, and connected them back to back. Here is how the backside looked like.
Comparing power ratings: fluorescent light bulb is rated at 13 Watts. For the LED lamp there are 10 strings, each string drawing 20 mA, for a total of 200 mA at 31 Volts = 6.2 Watts.

Comparing lifetimes: I am sure that the LED lights will outlive me. The fluorescent light bulb you see in the picture is the second one I bought.

Yard Lights

This project turned out to be the most successful. I had 10 yard lights, 4 Watts each, for a total of 40 Watts. Those light bulbs are shown on the left in the picture below.
The replacement LED lights are shown on the right. I used 4 LEDs per yard light, each pointing 90 degrees apart as shown in the picture. Four LEDs are connected in series, plus 68 ohm resistor. All the lights are powered by a small 12 VDC brick power supply. Total power = 20mA * 12 V * 10 = 2.4 Watts.

Probably because it is darker outside, the yard lights look very bright. Our yard lights are turned on 20 minutes after sunset every day by the computer (please see this post ).

Update as of Oct 16th, 2012

OK, I had ordered some LED lights for testing and now I have received both orders. Here is the results. The first order was for a 4 W 60 SMD E27 base LED light. There are two of them in the picture above with standard 60 W Phillips incandescent light bulb in the middle and a couple of coins in the foreground for size comparison. These 4 W light bulbs can be used to illuminate a picture on the wall or can be used as a desk lamp, but it does not give enough light to illuminate the whole room.

My second order was for a small LED corn light bulb to replace numerous decorative light bulbs that I had. I ordered only a couple for testing purposes, and I am glad that I did not order a whole bunch. The picture above shows four light bulbs with four different bases. From left to right, the first one is E27, the standard base. The second one is an old Christmas light, base E16. The third one is what I had ordered, 5 Watt 108 LED E14 base corn light. The last one (the decorative light bulb) is base E12, also known as candelabra base. The number after the letter ‘E’ shows the diameter of the base in millimeters.

The LED corn light gives enough light (especially a few of them at a time) to illuminate a small room and the light produced goes in all directions. So it is more like a regular light bulb. The problem is that it is only available in E27 base and E14 base. I ordered an adaptor to convert from E14 to E12, but then the light bulb becomes too long to fit in the light fixtures that I have.

Update as of Nov 14th, 2012

I ordered another LED light bulb candelabra base as shown in the picture below. These are 5W Candle Warm White LED light bulbs. The golden base is a metal heat sink. This light bulb fits in the chandelier just fine, however it does not produce enough light, and the light that is produced is directional. And more importantly, Lisa did not like it. (:

5W LED Candle Light

As far as the chandelier goes, I gave up on the idea of finding a candelabra base light bulb that will work in it, save energy, produce good enough light, and be acceptable to everybody.

Sometimes it is hard to beat the performance of a fluorescent light bulb compared to an LED light bulb. For example, our living room lamp used 150 Watt incandescent light bulb. We replaced it with a T9 30 Watt circular fluorescent light bulb (2700 Lumens?). It gives just as much light as before, and it looks nice. The only difference is that it uses 30 Watts instead of 150 Watts.

30 Watt Fluorescent

30 Watt Fluorescent

For the 100 Watt halogen lights, I installed a prototype LED light to see how it goes. It uses two 10 Watt power LED lights. This is in progress, not much to report yet. But you can see how it looks like in the picture below. The first three lights are 100 Watt halogen, the fourth one is the LED prototype.

2 x 10 Watt power LEDs, the fourth light is LED

Next Steps

I have ordered 15 more 10 Watt LED lights to replace some of the 100 Watt halogen lights. These lights require a separate power supply to operate them, and need to be mounted on a heat sink.